Re: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table per PCI segment

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 24 September 2019 10:10
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Andrew Cooper 
> <Andrew.Cooper3@xxxxxxxxxx>
> Subject: Re: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table 
> per PCI segment
> 
> On 23.09.2019 18:30, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
> >> Beulich
> >> Sent: 19 September 2019 14:25
> >> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> >> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Suravee Suthikulpanit
> <suravee.suthikulpanit@xxxxxxx>
> >> Subject: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table 
> >> per PCI segment
> >>
> >> Having a single device table for all segments can't possibly be right.
> >
> > The copy of the spec. I have says (on page 253: Fixed-Length IVHD
> > Blocks) that IVHD entries must have a segment group of 0, so can't
> > the code just require iommu->seg == 0?
> 
> The wording in my version is "At this time, only PCI Segment Group 0 is
> supported." This suggests to me that it is not a good idea to have logic
> baked in that depends on this remaining true. I realize though that there
> are more places than just this one where we (have to) assume segment 0
> (all in iommu_acpi.c, and all marked with an XXX comment).
> 

Ok. Fair enough. I just wasn't sure it was worth doing this change at the 
moment; but it doesn't hurt, so you can add my R-b.

  Paul

> Jan
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